Просто измените эту строку data: urlencodeFormData(formData),
и добавьте urlencodeFormData
эту функцию в конце.
$.ajax( {
type: 'POST',
url: wpcf7.apiSettings.getRoute(
'/contact-forms/' + wpcf7.getId( $form ) + '/feedback' ),
data: urlencodeFormData(formData),
dataType: 'json',
processData: false,
contentType: "application/json; charset=utf-8"
} ).done( function( data, status, xhr ) {
ajaxSuccess( data, status, xhr, $form );
$( '.ajax-loader', $form ).removeClass( 'is-active' );
} ).fail( function( xhr, status, error ) {
var $e = $( '<div class="ajax-error"></div>' ).text( error.message );
$form.after( $e );
} );
function urlencodeFormData(fd){
var params = new URLSearchParams();
for(var pair of fd.entries()){
typeof pair[1]=='string' && params.append(pair[0], pair[1]);
}
return params.toString();
}